Polarizerless electro-optic IR shutter based on a cholesteric scattering effect

Abstract

The light scattering effect of the focal-conic to homeotropic texture transition of a cholesteric liquid crystal has been exploited to develop an electro-optic liquid crystal shutter for visible and infrared light without the utilization of polarizers. Using small helical pitches, the passive decay time from the homeotropic to the scattering state has been minimized to a size in the order of 2 milliseconds which is necessary for a 50 Hz shutter operation. To get active rise times of the same size without too large an increase in the necessary addressing voltage, while maintaining a good scattering contrast, the remaining cell and material parameters have been optimized. Using CaF₂ substrates, the shutter can be operated in the near and middle infrared region. Its contrast gradually decreases with increasing wavelength.